This invention relates generally to the field of fuel dispensing systems, and, more particularly, to an improved fuel dispensing system using a dual rotor turbine flow meter.
Fuel dispensing systems used for highway vehicles and marine applications generally contain from one to eight flow meters and associated valves and dispensing hoses. One or more displays indicate the total delivered fuel quantity and the resultant sale price. Dispenser systems also provide one or more pumps to lift the fuel from underground storage tanks for delivery to the vehicle. The pumps are either mounted within the storage tanks or separate therefrom.
Multiple fuel grades, usually differing octane levels for gasoline, are often delivered from one dispenser. Diesel fuel is generally maintained in a separate piping, metering and delivery system.
Meters are typically positive displacement meters which utilize multiple pistons on a crankshaft to measure the volume of fuel passing therethrough. As fuel is forced through the meters, each piston is displaced thereby causing rotation of the crankshaft. Each stroke of the piston displaces a precise quantity of fuel. For each stroke of the piston, a number of electrical pulses is emitted from an encoding device mounted to the end of the piston shaft. The number of pulses is used to calculate the volume which has passed through the meter.
Piston meters as described do have some drawbacks. For example, seals employed in such meters are affected by the various chemical additives in the fuels. Over time and because of new additives blended into gasoline, the seals may deteriorate. Piston meters also tend to be quite large and bulky. Thus, packaging of up to eight meters in a single dispenser creates a very large dispenser.
Further, as ambient conditions such as the air temperature of the temperature of the fuel change, the internal dimensions of the piston meter also changes due to thermal expansion of the materials used to manufacture the meter thereby resulting in errors in the delivered fuel quantities reported. There is no known method for correcting this dimensional problem with piston meters.
While the inherent accuracy of the piston meter has been satisfactory for decades due to the relatively low price of fuel, as the price of gasoline rises, the need for ever improved accuracy increases. The piston meter may not be able to meet this need.
Further, state of the art electronics now afford an opportunity to predict and alarm a central station when a failure of the metering system is impending. However, piston meters do not have this capability.
Thus, there is a need for the use of a fuel dispensing system employing a new type of meter meeting these requirements. The present invention meets these needs.
It is an object of this invention to provide an improved fuel dispensing system having a meter which provides improved accuracy over piston meters.
It is a farther object of this invention to provide an improved fuel dispensing system which is much smaller than a piston meter with commensurate decline in the volumes of liquid contained therein.
It is still another object of this invention to provide an improved fuel dispensing system which includes the ability to predict impending failures of the metering system.
It is another object of this invention to provide an improved fuel dispensing system which is less sensitive to ambient conditions and which employs no seals to degrade performance over time.
Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.